Various systems are known for mounting a component or device on an instrument, machine or other object so as to protect or isolate it from external vibrational or shock forces. A foam rubber or other deformable pad placed under the component is one of the simplest arrangements. Alternatively, the component may be mounted with elastomeric grommets or isolators which typically include a hole through which a screw or other fastener is inserted to provide the component with a positive attachment to the surface on which it is mounted.
Disk drives used in computers, particularly small portable computers, are one type of delicate component which needs to be protected against external vibration and shocks. There are essentially two types of such disk drives, referred to as "dynamic loading" and "contact start/stop", respectively. In a dynamic loading drive, the actuator or carriage on which the read/write head is mounted is withdrawn to a position away from the disk when the drive is not operating. In a contact start/stop drive the read/write head rests at a "park" position on the surface of the disk (typically the inner portion thereof) when the drive is not operating.
In dynamic loading drives, the bearings of the spindle-motor are particularly vulnerable. A sizeable shock imposed on the drive can plastically deform or Brinell the races in these bearings. Such deformations in the bearing races may cause the disk to wobble in a lateral direction as it rotates (a condition referred to as "high runout") and may create tracking problems. Acoustic degradation caused by the clicking of the Brinelled bearing may also result. Moreover, Brinelling creates undue friction in the bearing and may slow down the rotation of the disk or prevent the disk from rotating altogether.
In contact start/stop drives, a shock on the drive may lead to "head slap", in which the head is lifted from and falls back to the surface of the disk. Similarly, if either type of drive is jolted during operation, the head may be forced through the thin boundary layer of air upon which it rides into sharp contact with the surface of the disk, a phenomenon known as "head crash". Either of these occurrences may damage the head and/or the disk.
These problems have become all the more common with the advent of "laptop" and "hand held" computers, which are often used in severe environments, being bumped or dropped repeatedly as they are moved from place to place. The disk drives in these computers are accordingly subjected to a variety of translational or rotary shocks.
To alleviate these problems, disk drives have typically been mounted with elastomeric grommets and screws or with isolators having studs attached to the ends. Both of these methods have disadvantages. First, grommets or isolators take up significant space, and space is at a premium in a small computer. Second, they involve several parts which must be assembled and installed. The extra expense arising from these steps can be substantial in the context of mounting a relatively small component such as a disk drive in a laptop, hand held or other miniature computer.
A third major disadvantage of conventional mounting techniques is that they generally permit purely translational (linear) shocks to be coupled into rotational shocks. This occurs because in general the resultant vector of the individual forces which are applied to the drive through the grommets or isolators when the computer is displaced suddenly in translation is not directed through the center of gravity of the drive. The drive therefore experiences a rotational moment of force as well as a translational force. This may be observed as a tendency of the drive to tilt or tip in the direction from which the force originates. Rotational shocks are particularly troublesome for disk drives that include rotary actuators or carriages because they tend to cause the rotary actuator or carriage to rotate about its pivot point, thereby risking potentially damaging contact between the read/write head and the disk or causing off-track errors during read and write operations. The only way to decouple the translational and rotational forces is to insure that the resultant of any translational force imposed on the drive will pass through the drive's center of gravity.